1. Field of the Invention
The present invention relates to an exhaust manifold for an engine, which is connected to a cylinder head of the engine for guiding an exhaust gas discharge out of a combustion chamber, and particularly, to an improvement in a manifold for an engine, including a manifold body which is comprised of a plurality of branch pipes and a common collecting chamber integrally connected to the branch pipes and communicating with an exhaust emission control device, the body being divided into an upper half and a lower half at a boundary face extending in a direction of arrangement of the branch pipes, the upper and lower halves being made of steel plates and welded to each other.
2. Description of the Related Art
In such a conventional exhaust manifold, a welding mating coupler is formed by the entire opposed edges of the upper and lower halves, for example, as disclosed in FIG. 6 of Japanese Utility Model Registration Publication No. 6-31140.
In the exhaust manifold having the above structure, a measure to limit any misalignment between the upper and lower halves in the direction of arrangement of the branch pipes is not taken. For this reason, in some cases, the halves may be misaligned from each other in the direction of arrangement of the branch pipes during welding in some cases and hence, it is difficult to efficiently produce an exhaust manifold with a small manufacture error. In addition, the mating coupler existing at opposed surfaces of adjacent branch pipes largely narrows a clearance between the adjacent branch pipes, resulting in a disadvantage that the mounting operation is impeded thereby, which operation involves coupling the exhaust manifold to the cylinder head by utilizing the clearance as a working space and the like.